JP2006327895A - Method for manufacturing compound semiconductor single crystal, vertical pbn vessel for the same, and method for selecting vessel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology by which a compound semiconductor single crystal can be manufactured in a stable and high yield. <P>SOLUTION: A vertical vessel 1b, made of pyrolytic boron nitride (PBN) and used for manufacturing the compound semiconductor single crystal, has an inner wall with which a droplet 2a of molten boron oxide forms a contact angle within a range of ≥80 and <140°. The compound semiconductor single crystal is manufactured by growing a GaAs single crystal or an InP single crystal by a vertical Bridgman method using the vessel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a manufacturing technique of a compound semiconductor single crystal, and more particularly to improvement of a technique of manufacturing a compound semiconductor single crystal using a pyrolytic boron nitride (PBN) vertical container.

  In recent years, various semiconductor devices using various compound semiconductor single crystals have been produced, and the demand for compound semiconductor single crystals has been increasing.

  The schematic cross-sectional view of FIG. 3 illustrates a manufacturing technique of a compound semiconductor single crystal disclosed in Japanese Patent No. 3216298 of Patent Document 1. In the vertical PBN container (also referred to as a crucible) 1 shown in FIG. 3, a boron oxide layer 2 is formed in advance on at least the inner surface of the installation portion of the GaAs seed crystal 3. Then, in the crucible 1, the GaAs polycrystalline raw material 4 is loaded on the seed crystal 3. When a GaAs crystal is grown from above the seed crystal 3 by the vertical Bridgman method or the vertical temperature gradient solidification method using the crucible in this state, the boron oxide layer 2 is fused with the GaAs melt in the gap between the seed crystal 3 and the container 1. It acts to prevent inconvenience that the liquid flows in and contacts the inner surface of the container to be polycrystallized. As a result, it becomes possible to grow a GaAs single crystal with improved crystallinity.

On the other hand, the schematic cross-sectional view of FIG. 4 illustrates a manufacturing technique of a compound semiconductor single crystal disclosed in Japanese Patent Laid-Open No. 2003-146791 of Patent Document 2. In FIG. 4, after a clean PBN crucible 1 is installed in a container such as quartz, the crucible 1 is heated to a high temperature in air by an electric furnace or the like. As a result, oxygen in the air reacts with the PBN material of the crucible to form a thin film 2 of boron oxide on at least the inner surface of the PBN crucible 1. In the crucible 1 in which the boron oxide film 2 is formed, an appropriate amount of boron oxide sealing agent 5 is placed above the compound semiconductor seed crystal 3 together with the polycrystalline compound semiconductor raw material 4. Thereafter, if the compound semiconductor single crystal is grown in the crucible 1, it is possible to prevent a coating defect due to the boron oxide film 2 on the inner surface of the crucible 1 and to obtain a compound semiconductor single crystal with improved crystallinity.
Japanese Patent No. 3216298 JP 2003-146791 A

  As disclosed in Patent Document 1 and Patent Document 2, if a boron oxide film is formed by previously oxidizing the region including at least the installation portion of the compound semiconductor seed crystal on the inner surface of the vertical container 1 made of PBN, Direct contact between the compound semiconductor raw material melt and the inner surface of the PBN container during crystal growth from the seed crystal is prevented, and an effect of reducing the occurrence of crystal defects in the grown crystal can be obtained. However, the effect is not perfect, and it is not easy to obtain a stable single crystal yield in the production of a compound semiconductor single crystal.

  Then, this invention aims at providing the technique which can manufacture a compound semiconductor single crystal with the stable high yield.

  According to the present invention, a vertical pyrolytic boron nitride (PBN) container used for manufacturing a compound semiconductor single crystal produces a contact angle of molten boron oxide droplets in the range of 80 degrees to less than 140 degrees. It is characterized by having an inner wall.

  A single crystal with improved crystallinity can be obtained in a stable and high yield by a method of producing a compound semiconductor single crystal using such a vertical PBN container.

  In the compound semiconductor single crystal manufacturing method, the vertical Bridgman method can be preferably used. As a compound semiconductor single crystal, a GaAs single crystal or an InP single crystal can be grown.

  In the present invention, the vertical PBN container is selected by collecting a PBN section from the upper end of the container, placing boron oxide particles on the surface of the PBN section corresponding to the inner wall of the container, and under an inert atmosphere. In which the boron oxide particles are melted to form droplets, and a container satisfying the condition that the boron oxide droplets generate a contact angle in the range of 80 degrees to less than 140 degrees with respect to the surface of the PBN slice is selected. It is characterized by that.

  By using the technique according to the present invention as described above, a compound semiconductor single crystal can be produced and provided with a stable and high yield.

  First, as a result of studying the reason why the compound semiconductor single crystal cannot be manufactured with a stable and high yield by the techniques of Patent Document 1 and Patent Document 2, the present inventors have formed PBN, which is a material of the vertical crucible, and the inner surface of the crucible. Due to the wettability with the boron oxide melt, it has been clarified that crystal defects occur when a boron oxide layer having a uniform and appropriate thickness is not formed on the inner surface of the crucible.

  That is, if the wettability of the inner surface of the PBN crucible with respect to the boron oxide melt is too good, the formed boron oxide melt layer hangs down below the inner surface of the vertical crucible and uniformly coats the inner surface of the crucible with an appropriate thickness. Can not be. On the other hand, when the wettability of the PBN crucible inner surface is poor, the adhesion between the boron oxide melt layer and the crucible inner surface is poor, and after the crucible is cooled to room temperature, the boron oxide layer formed on the crucible inner surface is missing. Cheap. Therefore, it is important that at least the inner surface of the vertical PBN crucible has an appropriate wettability with respect to the boron oxide melt, whereby a high yield of the single crystal can be realized in the production of the compound semiconductor single crystal.

  FIG. 1 is a schematic cross-sectional view of a vertical PBN container for explaining an embodiment of the present invention. The vertical PBN container 1 shown in FIG. 1 includes a main body portion having a diameter of about 100 mm and a height of 400 mm, and includes a tapered portion and a seed crystal holding portion below the main body portion. In this example, a large number of vertical PBN containers shown in FIG. 1 were prepared. Then, the contact angles of the boron oxide melt droplets on the inner surface of those PBN containers 1 were determined, and the vertical container groups AE were selected as shown in Table 1.

  The contact angle of the boron oxide melt droplets in Table 1 can be derived by the following operation. First, as indicated by a broken line in FIG. 1, the upper end portion 1a of the PBN vertical container 1 is cut out with a width of about 5 mm.

  As shown in the schematic side view of FIG. 2, the upper end portion 1 a cut out with a width of 5 mm is further divided into PBN sections 1 b of about 5 mm square. In a small sealed facility having a gas replacement mechanism and a heating mechanism, one boron oxide particle having a particle size of about 0.3 to 0.5 mm is disposed on one main surface of the PBN slice 1b. One principal surface is a surface corresponding to the inner surface of the vertical PBN container 1. Then, after making the inside of the small sealed facility a nitrogen atmosphere, the PBN slice 1b is heated to 850 ° C., and a boron oxide melt droplet 2a is generated. At this time, a side image of the boron oxide droplet 2a on the PBN slice 1b is taken. From this droplet image, the contact angle θ of the boron oxide melt droplet with respect to the surface of the PBN slice 1b is directly determined.

  As shown in FIG. 2, the contact angle θ is an angle formed by the tangent TL of the free surface and the surface of the PBN segment 1b at the point where the free surface of the boron oxide molten droplet 2a contacts the surface of the PBN segment 1b. As measured. However, the angle including the droplet 2a between the tangent TL and the surface of the PBN slice 1b is measured as the contact angle θ.

  The containers selected as shown in Table 1 were heat-treated at 1000 ° C. for 5 hours under an oxygen gas flow of 1 liter / min in a heat treatment furnace to form a boron oxide film on the inner surface of the container. Thereafter, the container was cooled to room temperature at 10 ° C./min while oxygen gas was continuously flowed.

  In this vertical container, a GaAs seed crystal having the <100> orientation as the axial direction was placed in the seed crystal holding part, and 10 kg of GaAs polycrystalline raw material and 130 g of boron oxide were sequentially accommodated. A vertical vessel containing this raw material was placed in a crystal growth furnace, and a single crystal was grown by a vertical boat method. That is, the temperature in the crystal growth furnace is first raised to melt and seed the polycrystalline raw material, and then the vertical vessel is moved at a speed of 5 mm / h in the furnace set at a temperature gradient of 10 ° C./cm to produce crystals. The training process was completed.

  In Table 1, the single crystallization ratio of the obtained crystal is shown. As can be seen from Table 1, when using a vertical PBN container having a contact angle of 80 degrees or more and less than 140 degrees (groups B, C, D), a high yield of 85% or more (single crystallization rate) A single crystal was obtained. On the other hand, when a vertical PBN container having a contact angle of less than 80 degrees was used (A), a single crystal yield of only 40% was obtained. Further, when a vertical PBN container having a contact angle of 140 ° or more was used (E), the single crystallization rate was as low as 50%.

  In this embodiment, the case where the crystal growth is performed by the vertical boat method is shown, but the same result can be obtained when the technique of the present invention is applied to the vertical temperature gradient solidification method. Moreover, although the result of GaAs single crystal growth was shown in the present Example, the same effect is acquired also when applying the technique of this invention to InP single crystal growth.

  As described above, based on the measurement of the contact angle of the boron oxide melt on the inner surface of the PBN crucible, selecting a PBN container capable of forming an appropriate and uniform boron oxide layer on the inner surface of the crucible by oxidation treatment. Can do. By using the PBN crucible thus selected, it is possible to prevent the boron oxide layer from being lost when the compound semiconductor polycrystalline raw material is charged into the crucible, and the yield of the compound semiconductor single crystal is drastically increased. Can be improved. That is, the quality of a PBN container suitable for compound semiconductor single crystal growth can be easily determined by examining the contact angle between the PBN crucible and the boron oxide melt without actually performing single crystal growth.

  As described above, according to the compound semiconductor single crystal manufacturing technique of the present invention, a compound semiconductor single crystal can be provided in a stable and high yield. Needless to say, the compound semiconductor single crystal can be used for manufacturing various semiconductor devices.

It is a typical sectional view of a vertical PBN crucible for explaining one example of the present invention. FIG. 2 is a schematic side view showing a contact angle of a boron oxide melt droplet on a section from an upper end portion of the vertical PBN crucible of FIG. 1. 1 is a schematic cross-sectional view illustrating a compound semiconductor single crystal manufacturing technique disclosed in Patent Document 1. FIG. 10 is a schematic cross-sectional view illustrating the compound semiconductor single crystal manufacturing technique disclosed in Patent Document 2. FIG.

Explanation of symbols

  1 Vertical PBN crucible, 1a PBN crucible slice, 2 boron oxide layer, 2a boron oxide melt droplet, 3 nitride semiconductor seed crystal, 4 compound semiconductor polycrystalline material, 5 boron oxide piece.

Claims (6)

  A vertical pyrolytic boron nitride (PBN) container used for manufacturing a compound semiconductor single crystal, and having an inner wall in which molten boron oxide droplets generate a contact angle in the range of 80 degrees to less than 140 degrees A vertical PBN container for producing a compound semiconductor single crystal.   A compound semiconductor single crystal manufacturing method comprising growing a compound semiconductor single crystal using the vertical PBN container of claim 1.   The method for producing a compound semiconductor single crystal according to claim 2, wherein the single crystal is grown by a vertical Bridgman method.   4. The method for producing a compound semiconductor single crystal according to claim 2, wherein a GaAs single crystal is grown.   4. The compound semiconductor single crystal manufacturing method according to claim 2, wherein an InP single crystal is grown.   The method for selecting a vertical PBN container according to claim 1, wherein a PBN section is collected from the upper end of the container, and boron oxide particles are placed on a surface corresponding to the inner wall of the container in the PBN section, A condition that the boron oxide particles are melted to form droplets in an inert atmosphere, and the boron oxide droplets generate a contact angle in the range of 80 degrees to less than 140 degrees with respect to the surface of the PBN slice. A method for sorting vertical PBN containers, wherein the containers satisfying the above conditions are sorted.

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